The purpose of this study is the area under the curve (AUC) for GB241 and rituximab concentrations.

Inclusion Criteria:

• having histologically confirmed NHL expressing CD20 antigen
• having obtained CR (complete remission) or CRu (uncertain complete remission) after the prior therapy
• signed an informed consent form which was approved by the institutional review board of the respective medical center
• aged from 18 to 75 years
• ECOG performance status of 0 to 1
• expected survival of at least ≥ 3 months

Exclusion Criteria:

• had received rituximab or other anti-CD20(+) monoclonal antibody treatment within 1 year before enrollment
• having to be at least 4 weeks beyond prior anticancer therapy including corticosteroid, or have not recovered from significant toxicities of prior therapy
• participating in other clinical trial within 30 days before enrolment
• with serious hematologic dysfunction (white blood cell count of <3.0×103/uL; absolute neutrophil count of <1.5×103/ uL; platelet count of < 75×103/uL; hemoglobin level of < 8.0 g/dL); hepatic dysfunction (total bilirubin level of > 1.5×ULN; aspartate amino transferase (AST) and alanine amino transferase (ALT) levels of >2.5 × ULN; renal dysfunction (serum creatinine level of > 1.5×ULN ); and International normalized ratio (INR) and partial thromboplastin time or activated partial thromboplastin time (aPTT) > 1.5 × ULN (unless on therapeutic coagulation)
• had received live vaccine within 4 weeks prior to study entry
• with other malignancies ; or central nervous system (CNS) lymphoma, AIDS-related lymphoma; or active opportunistic infection, a serious nonmalignant disease
• seropositive for HCV antibody, or HIV antibody, or hepatitis B virus surface antigen (HBsAg). HBc antibody seropositive, but HBV DNA and HBsAg negative patients may participle following consultation with a hepatitis expert regarding monitoring and use of HBV antiviral therapy, and provided they agree to receive treatment as indicated
• recent major surgery (within 28 days prior to study entry )
• with a history of allergic reaction or protein product allergy including murine proteins
• pregnant or lactating or not accepted birth control methods including male patients
• patients considered unsuitable by PI
• previous malignant tumor except cured cervical cancer,basal cell carcinoma and squamous cell skin cancer
• active opportunistic infections and other serious non neoplastic diseases